A US-based analysis done on three cohort studies determining the contribution of potatoes consumption in increased incidences of hypertension, was published in the British Medical Journal (BMJ) on May 17th, 2016. More than three or four servings of baked, boiled or mashed potatoes per week were found to increase hypertension in adults by 11%. An increase of 17% was recorded with regard to French fries consumption.
The researchers belonging to Brigham and Women’s Hospital as well as Harvard Medical School, examined the dietary intake of potatoes in more than 187,000 men and women for more than 20 years. The monitoring was carried out using food frequency questionnaires which recorded the information about the potato intake from three major categories: baked, boiled and mashed potatoes. These were considered as a single category whereas potato chips and potato crisps were assumed to be two separate categories. The blood pressure measurement was reported by the individuals themselves after being diagnosed by the healthcare professional.
The major finding of the analysis was that women who consumed four or more servings a week of baked, boiled, or mashed potatoes had an increased risk of high blood pressure in comparison to those who had less than one serving a month. However, taking French fries consumption into consideration, it was found that both men and women had an increased risk of high blood pressure. Potato crisps were observed to have no significant effect on the risk of high blood pressure in either men or women.
The possible explanation to the association between potato consumption and hypertension was scientifically explained in an editorial published in the BMJ. According to it, there are three major points which should be considered before singling out potatoes as the culprit i.e., the overall dietary pattern of the individual, the cooking method and the glycemic index of the food.
Mark Harris, Professor of General Practice and director of two leading healthcare centers, emphasized on focusing upon the dietary patterns rather than single food i.e., potatoes in this case. According to him, one of the major limitations of the study was the method adopted for evaluation in the cohort studies i.e., the food frequency questionnaire which does not specify the dietary pattern of the individual or the method of cooking. For instance, French fries were observed to raise the blood pressure levels but the overall salt consumption of the individual and the method used for cooking which entailed high salt usage was not justified by the food frequency questionnaires. Therefore, the recorded results regarding potato chips consumption were inconsistent.
Professor Harris backed up his argument by endorsing the ‘Dietary Approaches to Stop Hypertension’ (DASH) diet recommended by the US National Institutes of Health, which suggests including potatoes in the overall dietary pattern due to their effective role in prevention and control of hypertension. It should be noted that potatoes are high in potassium and low in sodium and fats, which makes them a good blood pressure lowering food.
Other than potatoes, the DASH diet includes meals rich in fruit, vegetables, whole grains and low-fat dairy foods, along with meat, fish, poultry, nuts and beans. It also dictates limited use of sweetened food products and drinks. Moreover, increased consumption of red meat and trans fats is also not recommended. The healthcare professional also emphasized on keeping a close check on the other food products consumed in a meal, along with potatoes. Moreover, it was discussed in the editorial that the glycemic load of the meal in totality is influenced by a number of factors and not a single nutrient of food. These varied factors include the protein and fiber content of the meal as well as the glycemic index of any other carbohydrate containing foods consumed in that meal.
Furthermore, the findings of the analysis can be justified by the help of an indirect mechanism which can possibly shed light on the hypertensive ability of potatoes. It should be noted that potatoes have a higher glycemic index than other vegetables, which triggers a rise in blood sugar levels. Foods that have lower glycemic index do not cause abrupt increase in the blood sugar and insulin levels. On the other hand, increased potato intake can lead to insulin resistance and higher insulin levels, leading to sodium retention in the body, which can then ultimately lead to hypertension over time.
The researchers while concluding their research work said that it had important implications for policy and practice, especially after the inclusion of potatoes as vegetables in government sponsored school feeding programs in the United States.
The researched stated that, “These findings have potentially important public health ramifications as they do not support a potential benefit from the inclusion of potatoes as vegetables in government food programs but instead support a harmful effect that is consistent with adverse effects of high carbohydrate intakes seen in controlled feeding studies.”
It was suggested that the overall pattern of foods offered in school lunch programs should be the focal point, rather than the isolated inclusion or exclusion of potatoes. Moreover, Professor Harris, while summing up the BMJ editorial said that the prospective cohort studies which assess the associations between various dietary patterns and risk of disease providing more useful insights for both policymakers and practitioners can serve as a useful tool rather than those studies which focus on individual foods or nutrients.